The coupling reaction of alkyl halides and Grignard reagents have been known for sometime. However, to couple aryl halides and cycloalkenes has not proven easy. In particular, the reactions for coupling aryl halides and cycloalkenes have been known to be slow, low in selectivity and are known to produce the desired product in low yields at best. Reactions which are known to produce coupling between an aryl halide and a cycloalkene, such as modifications of the Heck palladium-catalyzed cross-coupling of aryl halides and acyclic alkenes, in the past have employed elevated temperatures, tend to generate isomeric mixtures and are difficult to control and even then frequently provide low yields.
There is a real need for a direct coupling reaction between aryl halides and cycloalkenes to provide aromatic compounds with at least one of the nuclear hydrogen atoms replaced by an unsaturated cyclic hydrocarbon group. Such compounds are known to be useful as chemical intermediates in synthesis of wetting agents, detergents, bactericides, insecticides, resins and other organic compounds, as well. They are, in short, compounds of active interest. See, for example, U.S. Pat. No. 2,691,686 which issued Oct. 12, 1954, Bloch for Condensation of Aromatic Compounds with Cyclic Polyolefins. Also, for some of the difficulties of coupling reactions involving Grignard reagents and allylic halides see Cardenas U.S. Pat. No. 4,228,313 issued Oct. 14, 1980.
In accordance with the primary objective of the present invention, a mild, catalytic arylation of cycloalkenes is performed. This reaction is of considerable use in synthetic organic chemistry, as earlier outlined.
An additional object of the present invention is to provide such a reaction as above described which goes under mild conditions and provides a high yield of reaction product, generally in excess of 75% and at times in nearly quantitative yield.